Compared to infants born to mothers who conceived without assisted reproduction, those born following treatments like IVF were 25% more likely to have birth defects.

Researchers say the actual or "absolute" risk remains low overall.

The study, which was presented today in New Orleans at a national conference of the American Academy of Pediatrics, is not the first to show a small increase in birth defects among babies conceived through assisted reproduction.

“We don’t really understand why IVF raises the risk for birth defects,” says researcher Lorraine Kelley-Quon, MD, of UCLA Medical Center. “But we have now seen many studies from all over the world that show this association.”

Birth Defects More Common in IVF Babies

In the new study, Kelley-Quon and colleagues from UCLA’s Mattel Children’s Hospital used a statewide birth database to compare the incidence of birth defects among babies conceived through high-tech reproduction such as IVF and those born to mothers who conceived naturally.

The two groups of women were matched for characteristics including age, race, and previous births.

The birth defect rate for babies born through IVF or other high-tech fertility treatments was 9% compared to 6.6% for those conceived naturally.

Malformations of the eye, heart defects, and defects of reproductive organs and the urinary system were all more common among babies conceived through high-tech treatments.

Fertility treatments such as artificial insemination, intrauterine insemination, and use of fertility-enhancing drugs were not associated with an increased birth defect risk.

Infertility, Not Treatment, May Be to Blame

The researchers did not have information on which assisted reproduction treatments the couples in the study had.

In vitro fertilization typically involves attempts to fertilize in a laboratory and a transfer of the embryo back into the womb.

She adds that while it does appear that babies born following assisted reproduction have a small increased risk for birth defects, it is still not clear if the procedures are to blame.

It may be that infertility itself is a risk factor for birth defects, she says.

Avner Hershlag, MD, who is chief of the Center for Human Reproduction at North Shore-LIJ Health Center in New York, says if IVF and other forms of assisted reproduction do raise the risk for birth defects, the risk is small.

“It is important to do the research to answer this question,” he says. An estimated 5 million people were born using these techniques and the vast majority have no birth defects, he adds.

These findings were presented at a medical conference. They should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.